This invention relates to a microwave oven and, more particularly, to a wave seal of a microwave oven.
In a microwave oven, in which microwaves are radiated into a heating cavity thereof for heating objects placed therein, it is necessary to prevent the microwave from leaking to the outside of the heating cavity mainly through a gap created between two opposite surfaces, one being a wall portion defining an opening of the heating cavity and the other the wall of a door provided for closing the opening. Hitherto, a so-called choke seal has been employed to prevent such leakage of microwaves, as typically disclosed in U.S. Pat. No. 3,182,164. The choke seal is very effective in preventing the leakage of microwaves so long as the wavelength of the microwaves is not substantially changed from a specific design value. However, it does not satisfactorily prevent the leakage of microwaves if the wavelength varies to some extent from that value due to, for example, variation of the microwave oven. The load variation is a function of the quantity or property of objects being cooked in the heating cavity. The center frequency of the microwaves varies somewhat according to the condition of the load being cooked. Thus, the choke seal alone is not useful as a wave seal for the microwave oven, and it has been the practice to utilize it in combination with a different type of wave seal such as a capacitance seal, metal to metal contact seal or wave absorber, such as a ferrite-rubber. Such structure, however, inevitably introduces complexity in structure, high cost in manufacturing and inconvenience in use of the microwave oven.